The goal of this proposal is to gather preliminary data to test the feasibility and calculate the sample size for a larger study on the effects of age on skin protein turnover and wound healing in humans. [unreadable] [unreadable] Our general hypothesis is that dermal collagen turnover changes with aging and these changes are [unreadable] responsible for many of the alterations in skin function found in older adults, which may increase the risk of mechanical injury and delayed wound healing. Therefore, the measurement of dermal collagen turnover may be used as an objective tool to determine the effects of age on the skin, quantify the rate of wound healing, and test the effects of specific interventions aimed at stimulating skin regeneration and repair. Since collagen makes up the bulk of skin proteins, we further hypothesize that mixed skin protein kinetics can reliably reflect the turnover rate of skin collagen, and thus be used as a surrogate measure of skin collagen turnover. [unreadable] [unreadable] The specific aims of this proposal will be (1) to determine whether mixed skin protein turnover can be used as a surrogate measure of skin collagen turnover in human subjects, and (2) to determine whether skin protein synthesis is slower and/or breakdown faster in older subjects as compared to younger controls. [unreadable] [unreadable] To accomplish our aims we will simultaneously measure the synthesis and breakdown rates of mixed skin proteins, and the skin collagen synthesis rate in healthy human subjects using a new stable isotope method. [unreadable] [unreadable] The data obtained with this pilot project will be used as a basis for further studies (to pursue using the [unreadable] R01 mechanism) on the effects of aging on skin metabolism and wound healing. [unreadable] [unreadable]